108 American Fern Journal 



A. Leaf-blades of 3 nearly equal divisions, triangular, very thin; each 



division stalked and 1-3-pinnate 1. P. Dryopteris. 



A A. Leaf-blades not of 3 nearly equal divisions, not very thin. 



B. Leaf-blades oblong to lanceolate, 3-pinnate; rachis not winged. 



2. P. alpestris. 

 BB. Leaf-blades triangular, 1-2-pinnate; rachis winged. 



3. P. Phcgopteris. 



1. Phegopteris Dryopteris (L.) Fee. (PL 8, /. 3, 4.) 



Oak Fern. 



Rootstock slender, creeping. Leaves 12-18 inches 

 long; blade thin, 6-10 inches wide, composed of 3 

 almost equal divisions, glabrous or nearly so; primary 

 leaf-divisions again 1-2-pinnate, triangular, acute, their 

 leaflets or lobes crenate or entire. Sori small, round, 

 near edge of the leaflets or lobes. — In damp shady 

 forests. Alaska to New Foundland, south to Oregon, 

 Colorado and Virginia. 



2. Phegopteris alpestris (Hoppe) Mett. (PL 8 y /. 5, 



6.) 



Leaves tufted, 1-2 feet long; blade 2-4 inches wide, 



oblong to lanceolate, acuminate, 3-pinnate. Sori 



numerous.— British Columbia to Montana and Cali- 

 fornia. 



3. Phegopteris Phegopteris (L.) Underw. (PI 8, 

 *> 6.) 



Rootstock slender, creeping, scaly. Leaves 6-18 

 inches long; blade triangular, acuminate, 4-6 inches 

 wide, 2-pinnate, pubescent specially on veins beneath; 

 rachis winged. Sori near margin of leaflets.— Alaska to 

 Labrador, south to Washington, Iowa and Virginia. 



(To be Continued) 



